Tail rotor hub assembly for rotary wing aircraft

ABSTRACT

A tail rotor hub assembly for a rotary wing aircraft comprises a rotor hub having six radially extending arms arranged in three diametrically opposed pairs, each arm being adapted to support a tail rotor blade, the arms of each pair being staggered so that during operation the arms rotate in two separated planes, the staggered pairs being arranged so that alternate arms rotate one in each of the separated planes and groups of three arms rotate in each plane. The rotor hub and arms are of one piece construction, a common pitch change control mechanism is adapted for connection to all blades, and blade flapping control stops are integral with the rotor hub.

[ 5] Oct. 24, 1972 [54] TAIL ROTOR HUB ASSEMBLY FOR ROTARY WING AIRCRAFT[72] inventor: Peter John Flux, Somerset, England [73] Assignee:Westland Aircraft Limited, Yoevil, Somerset, England [22] Filed: Feb.10, 1971 [21] Appl. No; 114,299

[30] Foreign Application Priority Data Feb. 27, 1970 Great Britain..9,613/70 [52] US. Cl. ..416/123, 416/168, 416/198 [51] Int. Cl ..B64c27/08 [58] Field of Search ..416/107, 123,140, 141, 168, 416/198, 200,244

[56] References Cited UNITED STATES PATENTS 2,795,284 6/ 1957 Sikorsky..416/123 UX 3,232,349 2/ 1966 Ballauer ..416/ 168 UX 3,448,946 6/1969Nagatsu ..416/ 123 UX 3,470,962 10/ 1969 Cure ..416/244 UX 3,533,71310/1970 Salmun ..416/140 3,552,880 1/1971 Fischer ..416/141 X 3,589,8356/1971 Linden ..416/140 X 3,591,310 7/1971 Mouille ..416/141 X 3,592,5597/1971 Ward ..416/200 X Primary Examiner-Everette A. Powell, Jr.Attorney-Larson, Taylor and Hinds [57] ABSTRACT A tail rotor hubassembly for a rotary wing aircraft comprises a rotor hub having sixradially extending arms arranged in three diametrically opposed pairs,each arm being adapted to support a tail rotor blade, the arms of eachpair being staggered so that during operation the arms rotate in twoseparated planes, the staggered pairs being arranged so that alternatearms rotate one in each of the separated planes and groups of three armsrotate in each plane. The rotor hub and arms are of one piececonstruction, a common pitch change control mechanism is adapted forconnection to all blades, and blade flapping control stops are integralwith the rotor hub.

5 Claim, 2 Drawing Figures PATENTED um 24 m2 SHEEY 2 [If 2 TAIL ROTORHUB ASSEMBLY FOR ROTARY WING AIRCRAFT This invention relates to a rotorhub, particularly, but not exclusively, for accommodating a multiplicityof rotor blades for the tail rotor of rotary wing aircraft.

With the large number of roles in which rotary wing aircraft areexpected to be able to operate and the uprating of the engine or enginesto cater for such changes of operation, the need for an improved yawcontrol has become more apparent, for instance, the carrying of loadswhich necessitate the aircraft flying at its maximum all-up weight undertropical conditions at relatively high altitude has shown that existingtail rotor blades have to operate at a coarse pitch setting, therebyusing a higher percentage of the engine horsepower available withresultant lower efficiency.

Similar conditions exist when a rotary wing aircraft is used to towwaterborne craft under emergency conditions such as a breakdown at sea,when due to the position of the ship it would not be possible for a tugsimilar vessel to arrive in time.

Tests have been carried out on a multibladed tail rotor to check thetheory by bolting two rotor hubs together. This system provided usefulinformation but was mechanically unacceptable, firstly due to aconsiderable increase in weight which could be expected with a doublehub, and secondly a complicated pitch change mechanism of largedimensions. Other disadvantages resulting from the double hub were agreater degree of staggering of the blades than was necessary with theresultant difficulty of tuning each blade relative to the other blades.

This invention provides a rotor hub wherein these disadvantages havebeen eliminated.

According to the invention I provide a rotor hub for rotary wingaircraft, said hub supporting a multiplicity of radially arranged rotorblades, wherein each blade is offset to its preceding and followingblade and located on a radial centerline from the axis of said hub.

In a preferred embodiment of the invention the rotor hub is a singlepiece hub, preferably machined from a forging, with the blade rootattachment portions kept to minimum dimensions to enable the securingbolts to be located close to the main body of the rotor hub, therebyenabling the overall diameter of the blades to be kept to a minimumwithout affecting the span or the chord of the blade itself. This ismade possible by. the staggering of the blades which in certain cases ofoperation could result in a reduction of the rotor R.P.M. (revs. perminute), with a decrease in the tip speed of the blades producingimproved efficiency.

In another feature of the invention provision is made for theincorporation of feathering hinge mounts to enable changes of pitch tobe effected by rotation of the blades.

In a further feature of the invention blade flapping is provided bybearing hinges with limiting stops.

The invention will now be described with reference to the accompanyingdrawings, in which:

FIG. 1 shows a plan view in part section of the single piece hub, theblade attachment members and the pitch change mechanism, and

Referring to FIG. 1, the one piece hub is generally indicated at 10, andis manufactured from a single forging provided with six arms 21alternately staggered, each arm incorporating a housing 22 toaccommodate the flapping hinge needle rollers 14, bush 13 and bolt 12,which secures the radial blade attachment members 11 to the arms 21.

The degree of flapping of the radial blade attachment members 11 iscontrolled by stops 15 (FIG. 2).

The tail rotor blades (not shown) are attached at point 16 to featheringhinge mount 17 which forms part of the radial blade attachment member I1.

Changes of pitch or incidence of the blades are effected by rotation ofeach feathering hinge mount 17 by means of linkage 18 attached byuniversal joint 19 to lug 20 which is part of or integral withfeathering hinge mount 17.

Referring to FIG. 2 which shows a sectioned side elevation of the singlepiece hub indicated at 10, two of the six arms 21 which are part of thehub forging are shown with the relative stagger between one blade andanother. This has been kept to a minimum consistent with mechanicalefficiency, giving easy maintenance, for instance, any one of thesecuring bolts 12 can be removed without disturbing in any way thepreceding or following securing bolts.

The blade pitch changing linkage 18 already described is shown connectedto a beam member 24 attached to sliding shaft 25, this shaft passingthrough the hub itself. It will be noted that linkages 18 are of twodifferent lengths to provide correct symmetry in relation to beam member24. Each of the linkages are adjustable in length, and by this meanstuning of the blades is made comparatively easy. By the term tuning, wemean the adjustment of the basic pitch of each blade to give a balancedpitch change when such changes are applied collectively, and the dynamicbalancing of the blades.

It will be appreciated that modifications may be incorporated withoutdeparting from the scope of the invention, for instance, the shape ofthe single piece hub may be changed to suit any particular installationor power driving means.

I claim as my invention:

1. A tail rotor hub assembly for a rotary wing aircraft comprising arotor hub having six radially extending arms arranged in threediametrically opposed pairs, each arm being adapted to support a tailrotor blade, the arms of each pair being staggered so that duringoperation the arms of each pair rotate in two separated planes, thestaggered pairs being arranged so that alternate arms rotate one in eachof the separated planes and groups of three arms rotate in each plane.

2. A tail rotor hub assembly as claimed in claim 1 wherein the rotor huband arms are of one-piece construction.

3. A tail rotor hub assembly as claimed in claim 2 further comprising acommon pitch change control mechanism adapted for connection to all sixblades.

4. A tail rotor hub assembly as claimed in claim 3 wherein a portion ofthe pitch change mechanism passes through the hub.

5. A tail rotor hub assembly as claimed in claim 2, wherein bladeflapping control stops are provided in- FIG. 2 shows a sectioned sideelevation of the single tegral with the rotor piece hub, and the pitchchange mechanism.

1. A tail rotor hub assembly for a rotary wing aircraft comprising arotor hub having six radially extending arms arranged in threediametrically opposed pairs, each arm being adapted to support a tailrotor blade, the arms of each pair being staggered so that duringoperation the arms of each pair rotate in two separated planes, thestaggered pairs being arranged so that alternate arms rotate one in eachof the separated planes and groups of three arms rotate in each plane.2. A tail rotor hub assembly as claimed in claim 1 wherein the rotor huband arms are of one-piece construction.
 3. A tail rotor hub assembly asclaimed in claim 2 further comprising a common pitch change controlmechanism adapted for connection to all six blades.
 4. A tail rotor hubassembly as claimed in claim 3 wherein a portion of the pitch changemechanism passes through the hub.
 5. A tail rotor hub assembly asclaimed in claim 2, wherein blade flapping control stops are providedintegral with the rotor hub.